Data analysis Data were analyzed using the Statistical Package for Social Sciences version 12 (SPSS Inc. Chicago, IL USA). Results are presented as mean and standard deviation or median [interquartile range] for continuous variables and as count (percentage) for discrete variables. Proportions were compared by the Z test for two proportions, means by repeated measure ANOVA, paired t test or independent t test where appropriate and medians by the Wilcoxon rank sum test. Where necessary continuous variables were categorized using the median as cutoff. A p-value < 0.05 was used to characterize statistically significant results.